Yes -- GPS with cue sheet and/or map as backup in case something goes wrong.
Full disclosure, I've never done a randonee or brevet etc., but I frequently do long distance gravel events.
I resisted navigation devices for a long time, mainly because of concerns of battery life and other technological failures, and I'm pretty good at reading a map. However, I bought a Wahoo Bolt because of all the other features that I wanted, and since it has navigation anyway I started using it and I'm a total convert now. It's been flawless for me. But I still always have cue sheets and maps in my pocket as a backup because you just never know.
Side note: There are certain events where they refuse to provide GPS files as some sort of bizarre point of pride or honor or legitimacy. I don't agree with their logic and I won't participate in those events. The whole point of these events is a test of riding your bike -- not your land navigation skills. I'm perfectly capable of reading a map and I don't need a bike ride to prove that.